Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

2012

Thesis Director

Scott Meiners

Thesis Committee Member

Barbara Carlsward

Thesis Committee Member

Andrew Methven

Abstract

Vesicular arbuscular mycorrhizae (YAM) are the most common mycorrhizal fungi that form symbiotic associations with plant species. They form hyphae, vesicles and arbuscules which expand root surface area and exchange nutrients within root cells. Greater abundance of YAM can result in more nutrient uptake and disease resistance to the host plant. While mycorrhizae are often important to the growth and reproduction of individual species, their role in regulating plant community dynamics is less clear. Previous research has shown that YAM are tightly related to plant traits such as relative growth rate, foliar N and P concentrations, and responses to soil biota. Mycorrhizae can alter competitive outcomes among plant species and control the relative abundances of species, suggesting they may be important in community dynamics.

This study focused on the relationship between YAM and plant community dynamics by quantifying YAM colonization rates of a suite of plant species and linking these data with long-term vegetation data. Plant samples were collected from the Hutcheson Memorial Forest Center, New Jersey, the site of the Buell-Small Succession study, a long-term study of old field dynamics. Root tissue was collected from five individuals of 46 species to represent a range of successional positions (early through late), origins (native and non-native) and life forms (woody and herbaceous). Root samples were cleared, stained and examined at l00X magnification. Percentage of root length colonized by hyphae, number of vesicles and arbuscules were quantified within each field of view to capture the potential range of YAM infection in BSS plants. These data were then were related to plant trait data and long-term vegetation data to determine role of YAM in communities.

YAM infection varied dramatically among species and, somewhat between origins (native and non-native) and life forms (woody and herbaceous): non-native species having higher hyphal colonization than native species and herbaceous species having more vesicles than woody species. Principal Component Analysis (PCA) found associations between number of vesicles and other plant functional traits. However, there was little association between YAM measures and community dynamics. Of seven metrics of population dynamics, only one had a marginally significant association with a YAM measure: rate of decrease was correlated with number of vesicles within native species before the multiple comparison correction.

In general, YAM are strongly associated with plant individual growth and function in plant resource allocation strategies. Variations and patterns between YAM measures and plant functional traits and community dynamics traits had strong implications for YAM functioning as a potential regulator of plant community during succession, but were not strong enough individually to be linked with population dynamics.

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